Fish Types

Fish Types

Half-Spined Seahorse


Scientific Name: Hippocampus semispinosus
Family: Syngnathidae
Color: yellow, black, tan

Fish Care

Fish Diet: Carnivore
Aggressiveness: Non-Aggressive
Reef Safe: Yes
Minimum Tank Size: 30 gal
Max Size: 7"
Relative Care: Expert


Hippocampus semispinosus, commonly known as Half-spined Seahorses naturally occur in the Timor Sea from N.W. Australia to Bali where they prefer muddy substrate habitats in and around mangroves.

Male and female Half-spined Seahorses vary somewhat in color. Males can range in color from yellow to dark brown with splashes of white in their trunk. Females can range in color from yellow to dark red. In the wild, these seahorses may also have algae growth on their spine. Like all seahorses, the males birth baby seahorses in their pouch.

These social fish thrive when kept as a mated pair or in small groups in a species-only aquarium. A 30-gallon aquarium is sufficient for a single pair. Add 10 gallons to the size of the aquarium for each additional pair. Spray bars may be used to create gentle flow while eliminating stagnant areas in the aquarium. Seahorses are not strong swimmers, preferring to use their prehensile tails to hitch to branching live rock, algae, or artificial decorations.

Seahorses are less likely to contract Vibrio bacterial infections if the temperature is not allowed to exceed 74°F. This is particularly important if the aquarium contains other species of Syngnathids. It is also necessary to remove detritus and uneaten food daily. Calcium and alkalinity levels must be monitored and maintained to keep their bony plates healthy.

Half-spined Seahorses may be kept with small, shy fish such as small gobies, pipefish, dragonets, and firefish. However, aggressive, territorial, or fast-moving fish do not make good companions.

Seahorses can be harmed by anemones and corals with stinging tentacles or corals that are large enough to consume them, such as brain corals. While sea fans, Acropora corals, and other branching corals may be safe for seahorses, the corals can be irritated or damaged by a seahorse that continually hitches to them. Crabs and clams may pinch a seahorse causing a wound that could lead to secondary infections. Small ornamental crustaceans may be consumed by the seahorses.


Avoid fish that will out-compete Half-spined Seahorses for food. These captive-bred seahorses are accustomed to frozen Mysis shrimp, making them a smart alternative to their wild-caught counterparts. They will also feed upon amphipods and other small crustaceans found in live rock. Half-spined Seahorses will also accept vitamin-enriched adult brine shrimp , but this should not make up a majority of their diet. They are slow, deliberate feeders and prefer two or more small feedings per day.

Seahorses are probably the most recognizable fish in the world due to their unusual appearance and habits. They are very social, curious fish that are fun to watch while they interact with their surroundings, each other, and even their owners.

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